In the field of mobile communications, technological studies on multimedia broadcast/multicast service (hereinafter referred to as “MBMS”) are underway recently. Communications carried out in MBMS are not point to point (P-to-P) communications, but point to multi (P-to-M) communications. That is, in an MBMS, one radio communication base station apparatus (hereinafter referred to as “base station”) sends the same information to a plurality of radio communication mobile station apparatuses (hereinafter referred to as “mobile stations”) simultaneously.
The MBMS has a broadcast mode and multicast mode. While the broadcast mode is a mode in which information is sent to all mobile stations as with current radio broadcasting, the multicast mode is a mode in which information is sent to only specific mobile stations affiliating a news group or other services.
Advantages in carrying out the MBMS include the following: That is, when each mobile station receives information sent from a base station through a streaming service, etc., using one channel, if the number of mobile stations requesting the information increases, the load on the radio channel increases. However, when the MBMS is used, even if the number of mobile stations increases, all those mobile stations receive the information using the same channel, and therefore it is possible to increase the number of mobile stations capable of receiving the information without increasing the load on the radio channel. Currently, distribution of traffic information, music distribution, news distribution at a station, distribution of live coverage of a sport event, etc., are considered as services available using the MBMS and providing these services at a transmission rate of approximately 8 to 256 kbps is under study.
Here, when an attempt is made to provide high reception quality in an MBMS for a mobile station located on a cell boundary, this results in excessive reception quality for mobile stations located close to a base station, producing waste. In this case, transmit power of a signal to be sent to the mobile station located on the cell boundary grows extremely and causes a reduction of the subscriber capacity of the entire system as a consequence.